Timothy J. Kaufmann

A Prospective Trial of 3T and 1.5T Time-of-Flight and Contrast-Enhanced MR Angiography in the Follow-Up of Coiled Intracranial Aneurysms

BACKGROUND AND PURPOSE: Endovascularly coiled intracranial aneurysms are increasingly being followed up with noninvasive MRA imaging to evaluate for aneurysm recurrences. It has not been well-established which MRA techniques are best for this application, however. Our aim was to prospectively compare 4 MRA techniques, TOF and CE-MRA at 1.5T and 3T, to a reference standard of DSA in the evaluation of previously endovascularly coiled intracranial aneurysms. MATERIALS AND METHODS: Fifty-eight subjects with 63 previously coiled intracranial aneurysms underwent all 4 MRA techniques within 8 days of DSA. There were 2 outcome variables: coil occlusion class (class 1, complete; class 2, dog ear; class 3, residual neck; class 4, aneurysm filling) and change in degree of occlusion since the previous comparison. Sensitivity and specificity were computed for each MRA technique relative to the reference standard of DSA. Differences among the MRA techniques were evaluated in pair-wise fashion by using the McNemar test. RESULTS: For the detection of any aneurysm remnant, the sensitivity was 85%–90% for all MRA techniques. Sensitivity dropped to 50%–67% when calculated for the detection of only the class 3 and 4 aneurysm remnants, because several class 3 and 4 remnants were misclassified as class 2 by MRA. CE-MRA at 1.5T and 3T misclassified fewer of the class 3 and 4 remnants than did TOF-MRA at 1.5T, as reflected by the significantly greater sensitivity for larger aneurysm remnants with CE-MRA relative to TOF-MRA at 1.5T (P = .0455 for both comparisons). CONCLUSIONS: CE-MRA is more likely than TOF-MRA to classify larger aneurysm remnants appropriately. We recommend performing both CE-MRA and TOF-MRA in the follow-up of coiled intracranial aneurysms and at 3T if available.

Lack of Preoperative Spinous Process Tenderness Does Not Affect Clinical Success of Percutaneous Vertebroplasty

PURPOSE Some operators use the lack of point tenderness over compression fractures to exclude patients from undergoing percutaneous vertebroplasty procedures. The purpose of this study was to determine whether this lack of tenderness portends a poorer clinical outcome after vertebroplasty than is achieved in patients with such tenderness. MATERIALS AND METHODS The authors conducted a retrospective review of consecutive percutaneous vertebroplasty procedures performed at their institution to define two populations. Group 1 included 90 patients with tenderness to palpation over the spinous process of the fractured vertebra, whereas group 2 included 10 patients without such tenderness. This second group presented with back pain and demonstrated tenderness distant from the fracture (n = 5), tenderness lateral to the fracture (n = 4), or no focal tenderness at all (n = 1). All were treated because of edema seen on magnetic resonance (MR) imaging and/or increased activity on bone scan. Clinical outcomes were assessed by quantitative measurements of pre- and postoperative levels of pain (11-point scale) and mobility (five-point scale). RESULTS Pain improvement of three points or greater occurred in 77 of the 85 patients (91%) in group 1 who complied with follow-up and nine of nine such patients (100%) in group 2, with mean postoperative pain levels of 1.82 and 0.33 points, respectively (P =.14). Forty of 45 patients (89%) in group 1 with impaired preoperative mobility reported improvement postoperatively, as did two of three such patients (67%) in group 2. Mean levels of postoperative impaired mobility for groups 1 and 2 were 0.27 and 0.67 points, respectively (P =.27). CONCLUSION Pain on palpation over the fractured vertebra is not a necessary requirement in selecting patients who will benefit from percutaneous vertebroplasty. Other factors, such as MR evidence of edema or increased uptake on bone scan, should be weighed considerably in the decision to treat a patient.

Volumetric myelographic magnetic resonance imaging to localize difficult-to-find spinal dural arteriovenous fistulas

Although more prevalent in males in the 6th and 7th decade of life, spinal dural arteriovenous fistulas (SDAVFs) are an uncommon cause of progressive myelopathy. Magnetic resonance imaging and more recently Gd bolus MR angiography have been used to diagnose, radiographically define, and preprocedurally localize the contributing lumbar artery. Three-dimensional myelographic MR imaging sequences have recently been developed for anatomical evaluation of the spinal canal. The authors describe 3 recent cases in which volumetric myelographic MR imaging with a 3D phase-cycled fast imaging employing steady state acquisition (PC-FIESTA) and a 3D constructive interference steady state (CISS) technique were particularly useful not only for documenting an SDAVF, but also for providing localization when CT angiography, MR imaging, MR angiography, and spinal angiography failed to localize the fistula. In a patient harboring an SDAVF at T-4, surgical exploration was performed based on the constellation of findings on the PC-FIESTA images as well as the fact that the spinal segments leading to T-4 were the only ones that the authors were unable to catheterize. In a second patient, who harbored an SDAVF at T-6, after 2 separate angiograms failed to demonstrate the fistula, careful assessment of the CISS images led the authors to focus a third angiogram on the left T-6 intercostal artery and to perform superselective microcatheterization. In a third patient with an SDAVF originating from the lateral sacral branch, the PC-FIESTA sequence demonstrated the arterialized vein extending into the S-1 foramen, leading to a second angiogram and superselective internal iliac injections. The authors concluded that myelographic MR imaging sequences can be useful not only as an aid to diagnosis but also for localization of an SDAVF in complex cases.

Specificity of MR Angiography as a Confirmatory Test for Carotid Artery Stenosis: Is It Valid?

OBJECTIVE We believe that many studies in the literature show a falsely elevated specificity for carotid MR angiography (MRA) in the detection of high-grade stenosis. The purpose of this study was to test the hypothesis that inclusion of a substantial proportion of normal carotid arteries in a study population will falsely elevate the specificity of MRA for confirming a high-grade carotid artery stenosis. MATERIALS AND METHODS Seventy-seven carotid arteries were evaluated in 63 patients suspected of having a high-grade carotid stenosis, and all vessels were evaluated with contrast-enhanced MRA. Two subgroups were created, and the specificity of MRA was calculated for each group using digital subtraction angiography (DSA) as the gold standard. Group 1 included 44 vessels classified as high-grade stenosis on sonography and all were evaluated with DSA. To test our hypothesis, group 2 included the 44 carotid arteries from group 1 plus 33 carotid arteries classified as normal or minimally narrowed on sonography and MRA. RESULTS In group 1, the specificity of MRA for accurately confirming a high-grade stenosis was 29% for contrast-enhanced maximum-intensity-projection (MIP) images alone and 75% for contrast-enhanced axially reformatted source images as compared with DSA. When the 33 normal arteries from group 2 were added to the data set, the specificities increased to 70% and 89%, respectively. CONCLUSION The calculated specificity of MRA as a confirmatory test for high-grade carotid stenosis is highly dependent on the proportion of normal carotid arteries included in the calculation. Based on our results, the specificity of MRA reported in the literature has likely been overstated because of spectrum bias.

Dimpled appearance of a posterior communicating artery saccule: An angiographic indicator of arterial infundibula

2Department of Radiology, University of Michigan Health System, Ann Arbor, MI 48109. he diagnosis of cerebral aneurysm, especially in the setting of subarachnoid hemorrhage, remains of critical importance in patient management. Although angiography is considered by most practitioners to be the standard of reference in the diagnosis of cerebral aneurysm, uncertainty may arise in the region of the posterior communicating artery. Specifically, small, funnel-shaped dilatations of the proximal posterior communicating artery, termed arterial infundibula, may mimic aneurysms. Although rare reports exist of growth and rupture of infundibula, in most cases infundibula are not considered to be a source of subarachnoid hemorrhage. Thus, angiographic discrimination between infundibulum and aneurysm remains of critical importance. In this study, we describe the dimpled appearance on angiography of a saccule originating from the supraclinoid internal carotid artery (ICA) that we consider very suggestive of infundibula in contradistinction to arterial aneurysms. Specifically, the presence of a round radiolucency within an infundibulum during angiography, which may be transient, indicates wash-in of unopacified blood through a communicating artery. The clinical data and relevant imaging were reviewed for two patients who were found to have a dimpled appearance of a saccule originating from the supraclinoid ICA at cerebral angiography. Institutional review board approval was obtained for this study.

Laser ablation for mesial temporal epilepsy: a multi-site, single institutional series

OBJECTIVEAlthough it is still early in its application, laser interstitial thermal therapy (LiTT) has increasingly been employed as a surgical option for patients with mesial temporal lobe epilepsy. This study aimed to describe mesial temporal lobe ablation volumes and seizure outcomes following LiTT across the Mayo Clinics 3 epilepsy surgery centers.METHODSThis was a multi-site, single-institution, retrospective review of seizure outcomes and ablation volumes following LiTT for medically intractable mesial temporal lobe epilepsy between October 2011 and October 2015. Pre-ablation and post-ablation follow-up volumes of the hippocampus were measured using FreeSurfer, and the volume of ablated tissue was also measured on intraoperative MRI using a supervised spline-based edge detection algorithm. To determine seizure outcomes, results were compared between those patients who were seizure free and those who continued to experience seizures.RESULTSThere were 23 patients who underwent mesial temporal LiTT within the study period. Fifteen patients (65%) had left-sided procedures. The median follow-up was 34 months (range 12-70 months). The mean ablation volume was 6888 mm3. Median hippocampal ablation was 65%, with a median amygdala ablation of 43%. At last follow-up, 11 (48%) of these patients were seizure free. There was no correlation between ablation volume and seizure freedom (p = 0.69). There was also no correlation between percent ablation of the amygdala (p = 0.28) or hippocampus (p = 0.82) and seizure outcomes. Twelve patients underwent formal testing with computational visual fields. Visual field changes were seen in 67% of patients who underwent testing. Comparing the 5 patients with clinically noticeable visual field deficits to the rest of the cohort showed no significant difference in ablation volume between those patients with visual field deficits and those without (p = 0.94). There were 11 patients with follow-up neuropsychological testing. Within this group, verbal learning retention was 76% in the patients with left-sided procedures and 89% in those with right-sided procedures.CONCLUSIONSIn this study, there was no significant correlation between the ablation volume after LiTT and seizure outcomes. Visual field deficits were common in formally tested patients, much as in patients treated with open temporal lobectomy. Further studies are required to determine the role of amygdalohippocampal ablation.